Let a = i + j + √(2) k, b = b_1i + b_2j + √(2) k and c = 5i + j + √(2) k be three vectors such that the projection vector of b on a is a. If a + b is perpendicular to c, then |b| is equal to

Let a = i + j + √(2) k, b = b_1i + b_2j + √(2) k and c = 5i… — JEE Main 2019 Mathematics PYQ

JEE Main 2019 · 9 Jan · Shift II

Let

\mathbf{a} = \hat{i} + \hat{j} + \sqrt{2}\,\hat{k}

\mathbf{b} = b_1\hat{i} + b_2\hat{j} + \sqrt{2}\,\hat{k}

and

\mathbf{c} = 5\hat{i} + \hat{j} + \sqrt{2}\,\hat{k}

be three vectors such that the projection vector of

\mathbf{b}

\mathbf{a}

\mathbf{a}

. If

\mathbf{a} + \mathbf{b}

is perpendicular to

\mathbf{c}

, then

|\mathbf{b}|

is equal to

Show answer

Correct option: B

[JEE Main 2019 · 9 Jan · Shift II]

Practise Vector Algebra the way it is asked

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